Re: iridium 90 disappoints

From: Gerhard HOLTKAMP (
Date: Fri Sep 23 2005 - 17:23:01 EDT

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    Stephan Szyman wrote:
    >I went over to my grandparents' to demonstrate a prediction for iridium 90 
    >on 21 sept at 00:40:00 UTC.
    >HA predicted a flare of mag -7 for iridium 90 just near polaris.
    >it was the first time I have gone out to view a significantly bright iridium 
    >flare as predicted by HA only be disappointed.  at its peak it reached 
    >perhaps mag -1.5.
    >any ideas as to why this may have occured?
    Iridium 90 is 100 km below the operational Iridium orbits. I guess it acts as 
    a spare. Therefore its attitude does not have to be as tightly controlled as 
    those of the operational Iridium sats. A small change in attitude can lead to 
    a significant change in flare magnitude.
    Gerhard HOLTKAMP
    Darmstadt, Germany
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